Welcome to tech Stuff, a production from I Heart Radio. Hey there, and welcome to tech Stuff. I'm your host job in Strickland. I'm an executive producer with I Heart Radio and How the Tech are You? I am working right now on a couple of things. When I'm working on getting over COVID, I'm almost there, not quite there, but I'm getting there. And the other thing I'm working on is an episode about a company called San Sui that is a or was rather a company that made audio equipment like amplifiers and receivers and stuff like that. But as I was doing it, I felt like I was retreading some ground on a on a previous episode called how Speakers and Amplifiers Work? And I thought, why not have that episode play out? And then next week's Monday's episode will be about San Sui, and I won't have to to cover quite as much of the same territory again. I can focus more on the company in its history because y'all know me. Y'all know that if I start talking about a company that makes a certain kind of tech or sort of a product that features certain tech, I'll end up talking about how the tech came about what it does all that kind of stuff, but I've already done that. So we're gonna listen to this episode how speakers and amplifiers work, and I'll be back at the end to kind of tease next week's episode on this topic. But sit back and enjoy this classic episode. Today we are going to continue our episodes about how speakers work and how they are able to take electricity and make those sweet, sweet sounds for your ear holes. So let us jump back with a quick explanation of the electro magna at is um. So, electricity and magnetism are very closely related, and you've likely done the simple physics exercise of creating a basic electro magnet. So you'll take something like an iron nail and you'll wrap insulated copper wire in a coil around the nails several times. The nail acts as a ferromagnetic core. The copper wire coil is a conductor, so connecting the ends of the copper wire to a battery will then allow current to flow through the wire. Middle flow from one end of the battery through the wire down into the other end of the battery. As it goes around this coil, the flow of electricity creates a magnetic field, the nail and coil will behave like a permanent magnet. Would it's an electro magnet, but it will behave like a permanent magnet with a north pole and a south pole. And if you brought it close to a permanent magnet, then the opposite poles would attract each other and the similar poles would repel each other. So if you brought the electromagnets more poll next to a permanent magnets north pole, it would push that other magnet away and the polls will not change. Because the source of electricity is a battery, and batteries provide direct current, which means the current is always going to flow in the same direction. It's never going to reverse. But if you hooked the same nail and coil up to a source of alternating current, things would be very different. With alternating current, the direction of the flow of electricity changes rapidly every second, and as the direction of electricity changes, it affects the magnetic field. With electricity flowing in one direction, the head of the nail might represent the north pole of the magnet, and when the electricity switches to the other direction, the head of the nail will become the south pole of the magnet, and vice versa. You have created a fluctuating magnetic field by running an alternating current through an electro magnet, and you can do some pretty cool stuff with a fluctuating magnetic field. For example, if you bring this apparatus close to a conductive material, you'll induce a change of voltage in that material, even without making physical contact between the two. So if you do this with a stable magnetic field, all you'll do is see a very short spike, but then it stops because the magnetic field is not fluctuating. To induce electricity to flow by changing voltage in this other conductor, the magnetic field has to be fluctuating, or the conductor has to be moving in and out of the magnetic field constantly. If you get two coils of copper wire and you make sure the second copper wire has twice as many coils as the first one, you can create a transformer. So imagine you've got your first coil of wire. Let's say it's got ten coils ten ten loops around its core, and you've got a second core with copper wire, but there are twenty loops around the second core if you run a current through the first coil, it will induce current to flow through the second coil. Moreover, the voltage in the second coil will be higher than the voltage in the first coil because the second coil has twice as many coils as the first one. So the more times you loop a wire around a core, the greater the change of voltage is going to be between coil number one and coil number two. This particular version of a transformer would be called a step up transformer because the secondary coil has more turns than the primary coil and steps up the voltage. If the opposite were true, if coil number one had ten coils or ten loops and coil number two had five loops, then that would be a step down transformer. You would lower the voltage from primary to secondary. Transformers are what made alternating current the more viable solution to supplying electricity to homes and businesses back in the early days. Because transmitting electricity was all about efficiency. How could you efficiently get electricity from a power plant to where it needed to be well? If you used alternating current, you could create transformers and you could step up the voltage to very high levels, and that meant that you could transmit power across power lines much more efficiently. If you didn't do that, you had so much power loss that you would have to have lots of different power generators throughout the region in order to supply all the power needs of your area, at least back in the old days of direct current, because it wasn't easy to step up the voltage. And again, high voltage makes it more efficient to transmit power across long distances, so in the early days, that's why a C went out over d C. These days, you could actually do things a little differently if you wanted to, and you could go with direct DC power if you really wanted to, but it would require a big overhaul of the infrastructure. But transformers made a C much more practical anyway. Electromagnets are pretty awesome now. With speakers, it's not so much about voltage and current as it is about making the diaphragm of the speaker move in precise ways. With speakers, the electrical current acts as both the carrier of information and the means to make the diaphragm move. So you start with a steady magnetic field inside the basket You can create that steady magnetic field either with permanent magnets like I mentioned before, or with electro magnets, but it remains the same no matter what. The north pole is always going to be the north pole. The south pole is always going to be the south pole. Inside the frame, that field does not change. The voice coil on the cone ends up receiving the variable current that came from the transmitter that represents the recorded sound. Now, remember the way we record sound, as we typically will something like a microphone, and a microphone is essentially a speaker in reverse. A microphone has a diaphragm in it that vibrates in the presence of sound waves. Those vibrations cause fluctuations inside an electric current. You might vary the resistance of the circuit, as we talked about with the the old Johan Philip Rice approach, and by varying those that electric resistance within the circuit, you can fluctuate the electric current and then you can send that to a speaker, though you would typically send it to an amplifier first, but we'll talk about that in a minute. The speaker then essentially reverses this process. It takes those fluctuations sends them through an electro magnet, which will generate a variable magnetic field in response, which then makes the cone vibrate within the speaker and essentially do the opposite of what the microphones diaphragm was doing and recreate the recorded sound. It's pretty cool and pretty elegant, really. So the electrical signal representing the recorded sound comes into the speaker, feeds into the voice coil creates this fluctuating magnetic field. The field interacts with the permanent magnetic field inside the basket, either pulling the diaphragm forward in the basket and us pushing air outward, or pulling the cone back towards the back of the basket and allowing air to come further in by creating that lower pressure. And these fluctuations happen at high frequencies, so the diaphragm is moving very rapidly inside the basket. It's not just pushing out then pulling in. It's doing this hundreds or thousands of times per second, and it increases or decreases the air pressure as the cone pushes those air molecules or suddenly moves away, creating more space for them. And because sound is vibration. Those air molecules carry the sound up to our ears, and then we rock out to a C d C or whatever band you happen to like. That isn't nearly as cool as a C d C. Now, keep in mind what I have described is how a driver works. A speaker can and often does have more than one driver, and drivers come in different shapes, sizes, and purposes. So let's talk a little bit about what those are and what they do, and why you need to have different ones in the first place. Actually, that last question is the easiest answer right away. Remember again, sound is vibration, and low frequency sounds have longer wave forms. The points of high and low pressure are further apart from each other than with high frequency sounds. If you could actually see the changes in air pressure due to sound, you would see that the low frequency sounds have these larger gaps between the high and low pressure points in the waves as they move out from the source of sound. So you need a cone diaphragm that can vibrate at a slower frequency and push air effectively at that speed. For that reason, you would typically go with a heavier, larger diaphragm, both because the wavelengths of sound are longer if you're looking at the lower frequencies, and because making the material heavy gives it greater inertia, it takes more force to move of the diaphragm, and it will move at a pace that will reproduce as low frequency sounds you want. This type of speaker falls into the whooffer or sub whiffer categories. These are the speakers that create the base sounds. A sub whiffer tends to handle frequencies from around twenty hurts to two hurts. Think of a hurts as how long it takes a wave to pass through a given point in one second, or how many waves can pass through a given point in one second. Al Right, guys, we got some more to chat about with speakers. Before I jump into that, Let's take a quick break to thank our sponsor. Human hearing ranges from twenty hurts, which is twenty waves passing a given point in one second, to twenty killer hurts or twenty thousand waves passing through a point in one second. This really tells you more about the wavelength of the wave itself and thus the frequency and then the pitch. Remember, the lower frequencies are the lower pitches. The higher frequencies are the higher pitches, and that's the frequency range for typical human hearing twenty hurts to twenty thousand hurts. Now, I can tell you from my experience using a frequency sweeper, which will slowly go through a selection of frequencies that is all set at the same volume, so you get a standard volume across all of them, that while I can technically hear stuff at twenty hurts, it's not until you hit a frequency of about fifty hurts that it quote unquote sounds loud to me, even though actual volume of the two tones remains the same, so the amplitude is exactly the same, But until you get to a frequency of about fifty hurts, it just doesn't sound loud to me because my ears are not great at picking up those lower, super low frequencies. Also, I should mention that while sound waves come in different frequencies, sound itself travels at a speed that is dependent upon the medium through which it travels. So, in other words, low frequency sounds and high frequency sounds travel at the same speed through the same medium. Otherwise you would have all the high pitched sounds hitting your ears before the low pitched ones and conducting an orchestra would drive you crazy. The speed of sound is defined as the distance traveled by a sound wave in a certain unit of time. But hey, Jonathan, some of you might be saying you were just talking about frequencies. If a high frequency sound has twenty sound waves pass a certain point in the second, and a low frequency sound has twenty waves passing that same point in the second, are they traveling at different speeds? No, they're not. This is easier to imagine if we take an analogy. So let's say you're standing on the side of the road. Every single vehicle going past you on this one way road is traveling at a smooth twenty miles per hour or about thirty two kilometers per hour if you prefer. But they're all going that speed. Doesn't matter what kind of card is, they're all going exactly twenty miles or thirty two kilometers per hour. Some of these vehicles are very tiny, little smart cars. Some of them are super long extended buses, but they're all traveling at that same speed. So even though they're going at the same speed, the buses take more time to pass you than the smart cars do because the buses are longer. In the time it takes one super long bus to go buy you, like the front passes you and you time it out. Maybe for smart cars could go buy you and that same amount of time, even though they're all going at twenty miles. The same is true with sound waves, so we're not just talking about speed but wavelength. So low frequency sounds and high frequency sounds are traveling at the same speed. It's just you can fit more of the waves in at that time than others because of the length. All right back to the speed of sound. Now, I cannot give you a standard speed of sound for all occasions because the speed of sound depends on a lot of little things, For example, how much moisture is in the air or how cold is the air. Sound passes through the air, and air is made up of gases, and gases are made up of molecules. So as you heat up a gas, the molecules move apart from each other and they bounce around more. They're more able to move. As gas is cool, the molecules pack around together and they move around less, so they get more tightly packed. So a cold gas will transmit sound at a slightly slower speed than a warm gas will. If the temperature outside is sixty eight degrees fahrenheit or about twenties celsius and the air is dry, sound will travel at one thousand per second or three forty three per second. And it doesn't matter what frequency sound waves you're working with, that's the speed they're going to travel at. And again, at different temperatures and there are different media, sound will travel at a different speed. All right. Now, let's go back to the different types of drivers. After you handled the sub whoffers and the whoofers, well, the whoffers will still handle lower frequencies, but subwhiffers are are specialized whoffers, largely because they will frequently be paired with special circuits and cabinets dedicated to creating those very very low frequencies in an effort to produce a specific quality of sound, such as let's say you're watching an action film and something done blowed up real good. You want to have that rumbly low base for those moments, you know, the kind where you can actually feel it because it's vibrating the chair and the air around you, and so it's it's that kind of rumble you can feel in your chest. Well, that frequently means you need a dedicated subwhoffer unit that has its own power supply to generate the vibrations with enough force necessary to create that effect. So it's not just the speed but how hard it's pushing. After subwhiffers and whoffers, you've got mid range drivers or mid range speakers, and as the name suggests, these drivers are responsible for producing sounds in the middle range frequencies of human hearing. A typical range might include two fifty hurts to two thousand hurts. You may have also the term squawker when referencing mid range speakers. They're made of lighter materials and they can vibrate at higher frequencies than whiffers and subwhiffers, which is necessary to create those mid range tones. And then you have tweeter speakers. These are made of the lightest weight material and they vibrate the fastest in an effort to reproduce frequencies on the upper levels of human hearing, which tends to be between two thousand and twenty thousand hurts at least for consumer speakers. There are tweeters that can be made for special purposes that can generate sound frequencies well above the range of human hearing, some of them as high up as a hundred kill hurts or one hundred thousand hurts. That's five times higher than the highest frequency the average human is capable of perceiving. So why would you want a tweeter that could go beyond the range of human hearing. Well, you might use it for scientific research purposes, like finding out what high high high pitches the ultrasonic pitches might due to affect animal behavior. So you might be able to do that to learn how high a pitch a dog might be able to hear, for example, because dogs can hear at a different range than humans can. Or you might want to do experiments to see if those imperceptible frequencies have an effect on the sounds we can here. So there are audio files who insist that frequencies beyond the human range of hearing can change the quality of the sounds that we do here, and thus it's imperative to get a sound system and a type of media capable of reproducing sound frequencies at every level if you want a true reproduction of an original sounds quality. This falls into the realm of psychoacoustics the study of sound perception. Because hearing involves processes in the brain, there is a subjective component to it that cannot be easily described through physics. We can talk all about the physics of sound waves and sound propagation, but ultimately, when it comes to the way we experience sound, we have to take gray matter into account, and that gets tricky since our experience of perceiving sound can depend upon other things unrelated to the actual physics of the sound itself. For example, if I were to tell you that I have a sound system, and I've set it up and it consists of the most expensive and most technologically advanced components, and the media that was going to play represented the most true reproduction of an actual sound, that might be enough to influence your perception of the sound. Even if what I was really using was just good equipment, not the best, but just good stuff. Even if all all that stuff I told you wasn't true, your perception of sound might make it seem like you're listening to the most perfect reproduction of the original performance as could be attained. Or if I did play a sound back on what really was an amazing sound system, but Before I did it, I made a whole bunch of apologies for how the system I was using could not faithfully represent high tones, or had a very weak base output, or something like that. You might perceive the playback as fall lewing these trends that I had mentioned, even if scientific recording instruments were to show that the playback didn't suffer from those problems at all. All that being said, the psychological aspect of how we perceive sound does have limitations. No amount of snake oil salesmanship is going to convince you that a truly subpar stereo system is capable of reproducing the glory of the Philharmonic Orchestra, for example. But because there is the subjective element and how we perceive sound, there's the opportunity to exploit that element and make a lot of money in the process. I've talked before about how certain manufacturers have used this to market high end audio equipment, and some of that has little to no scientific evidence to back up the claims that they make about those gadgets, and yet they're able to set exorbitant prices for components that audio files will cover it because they're always in a quest to get that perfect representation of a sound. Uh, so this stuff does happen. I also covered this when I talked about MP three compression, because if you remember an MP threes, part of the compression strategy is to take all the different parts of a sound that we humans typically don't notice, and you just cut them. You get rid of them, because that way you cut down on the size of the sound file. The strategy is, if you can't perceive it, then we don't need it in the information. We can just cut it that. Audio files say no, if you do that, it affects the stuff that we can here, and thus you are changing the nature of the audio recording. Just because you couldn't hear the thing doesn't mean the thing wasn't doing something else. I think the jury is still out on that in a large part. I mean, there are some legitimate arguments to make about harmonics and things that do come into play, but I'm not sure it gets to the level of subtlety that a lot of audio files argue. At least I don't see the scientific evidence supporting it. That doesn't mean it's wrong, It just means I haven't seen the evidence supporting it. Anyway, As soon as we come back. I'm gonna go into talking about amplification and why that's important, but first let's take another quick break to thank our sponsor. All right. Now, Back when I was talking about the development of the loud speaker, I mentioned that Rice and Kellogg observed there needed to be advancements in amplification, and by that they meant there needed to be a way to boost the electrical signal from the risk the transmitter the microphone in order to give a speaker enough umph to vibrate at a force strong enough to play back the sounds at a suitable volume. Without amplifiers, the signal strength might only allow a speaker to play back a sound at a low volume, or if the signal is very weak, it might not even move the speaker significantly enough at all to create any real sound. The reason the signal tends to be weak goes back to the limitations we face when we record sound in the first place. So using the microphone effect, we transform sound into electrical signals by making the microphones diaphragm vibrate, mimicking the way our ear drums work. Right, So it's like we're speaking into someone's ear. When we talk into a microphone. Then we transform sound into electrical signals by making that microphone diaphragm vibrate, and those small vibrations introduce fluctuations into an electrical signal in some way. But for sound to affect the diaphragm at all, the diaphragm has to be very lightweight, very sensitive, and it has to make very small movements. Otherwise we'd have to make sound an enormous amplitudes or volume in order to generate the force necessary to vibrate the diaphragm. So it has to be very lightweight, very very sensitive, and it's moving in a very small distance, so it can only make tiny changes in electrical current or generate a very tiny electrical current. Now that's good enough for the purposes of recording the sound. You can do that. You can use that to record sound. It's fine because it can record at those tiny details. But if you want to play the sound back on a speaker, you have to boost that signal in order to drive the speakers to physically move them. You want to make the signal more powerful, but you also want to keep all the fluctuations of the signal, all the dynamics of the signal, So that way, you can represent when a song gets louder or more quiet, or when one element is taking over over another element. All of these things are very subtle, and you have to preserve that. So you want the signal not just to be boosted, but for all the different fluctuations of that signal to be represented in that boost. You want it all to be at the same relative strength as they were in the weaker signal. Now, an amplifier does this through the use of two separate circuits. The first circuit is the input circuit. That's the weaker of the two signals, that's the one that's coming from the microphone. The second circuit is your output circuit, which sends a stronger signal out to this speakers, and it draws upon the amplifier's power supply to boost the signal. So you have an amplifier, it has its own power supply. It's generating the signal that's going through this output circuit. The power going through the output circuit is a direct current, so it's flowing in a set direction. It does not change. If you have an amplifier and you've hooked it directly up to your house, is alternating current there's a power supply element inside the amplifier that converts it from alternating current to direct current. Now, think of the output circuit as always pushing a strong signal out towards the speakers. It's just most of the time this signal is not carrying any information. But when the amplifiers on, that's what's doing. It's pushing the strong signal out to the speakers. The input circuit's job is to use the original weak electrical signal as a way to vary the resistance in the output circuit, so the variable resistance recreates the voltage fluctuation in the original signal. So what you're doing is you've got this strong signal going out, use the weak signal to introduce the same fluctuations into the strong signal, and then the strong signal will reflect the weaker one. It will be exactly the same, except stronger. In the good old days, amplifiers relied upon vacuum tubes as an integral component, and in fact some amplifiers still do, particularly for stuff like professional electric guitar amplifiers. There are professional musicians who swear by vacuum tube amplifiers and they will not use anything else. Vacuum tubes are pretty interesting technology, and they date back to the early twentieth century. So let's talk about how they work for just a second. First, they look a lot like light bulbs, and in fact they operate very similar to light bulbs. They are glass tubes. Inside this glass tube is a filament like a light bulb. The filament inside uses electrical resistance to heat up. The filament either content aines or is somehow wrapped around a material like tungsten, which, when it's heated to very high temperatures, starts to boil off electrons. That would be the cathode of the vacuum tube. It's the source of electrons. The electrons accept only so much energy, and then after that they effectively jump ship. They're ready to burst off of the atoms that they were previously connected to. Now, also inside the vacuum tube is a plate that has a relative positive charge to it compared to the cathode. That's called the anode. The electrons are negatively charged, and so they're attracted to the positively charged anode, and the negative charged electrons flow towards the positively charged anode. Now, if this were all, there were to a vacuum tube, it would just be a diode. That means it would be an element in a circuit that would allow electricity to pass one way from the cathode to anode, but not back the other way. However, there's a third element, and that's what creates the amplification sho effect. That element is a grid of spiral wires or a mesh material. The acts as a sort of control grid or cage between the cathode and the anode, so it essentially surrounds the cathode. Now, if you apply a voltage to this control grid that is lower than the cathode itself, it reduces the amount of current passing from cathode to anode. By placing a large positive voltage on the plate and then feeding a signal to the control grid, you can affect the voltage across the load on the circuit. So you make tiny changes in the control grid's voltage and you get a much larger change across the load of the circuit amplifying the signal. So again, you you put a large positive voltage on this plate, you feed the input signal into the the control grid, and then you amplify that signal across the entire load, and that load would it typically involve speakers or an amplifier or These days most amplifiers do not use vacuum tubes. Instead, we use solid state transistors. To describe all those transistors work gets a little complicated, but in general, and basic transistor has three components. You've got an emitter, a base, and a collector. The emitter and the collector are both in type UH semiconductors, meaning that they have more electrons. They have a surplus of electrons there. You can think of it almost like a negative charge. The base is a P type semiconductor. It's sandwiched between the emitter and the collector. It has what would we would call a positive charge or holes for electrons. Feeding the input current between the emitter and the base creates a much larger output current between the emitter and the collector, thus amplifying the signal. Now, the output signal should ideally match the input signal exactly, except again everything is just bigger as an amplified and that signal would be strong enough to do the work of moving those speaker diaphragms and generating the sounds we enjoy. Well, I hope you enjoyed health speakers and amplifiers work. Like I said, next week we're going to have the story of San Sui and it's rise and fall and what the company did and UH the various products that it produced and why they were important. Why certain audio files to this day, we'll seek out San Sui UH components like receivers in particular, there's certain receivers that are highly prized among audio files. Even though spoiler alert, this company doesn't exist anymore. So that will be next week's episode. But I'm glad that I did this so that way you know, I'm not just repeating something I've already done in the past. I know that can be very frustrating, and due to my terrible memory, it happens pretty frequently without me even being aware of it. So I hope you enjoyed this episode. If you have suggestions for future topics, because San Sui is actually going to be that's a listener request. I'll talk about that more next week. So if you have a request, like if there's a specific topic in tech you want me to talk about. Maybe it's a particular company, a trend in technology of particular type of tech, and you want to know more about it, send me a message. I love getting those. It always gives me a great starting point to jump into some research, and the best way to do that is to send it over on Twitter. The handle for the show is tech Stuff hs W and I'll talk to you again really soon. Tech Stuff is an I Heart Radio production. For more podcasts from my Heart Radio, visit the i Heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.

Welcome to tech Stuff, a production from I Heart Radio. Hey there, and welcome to tech Stuff. I'm your host job in Strickland. I'm an executive producer with I Heart Radio and How the Tech are You? I am working right now on a couple of things. When I'm working on getting over COVID, I'm almost there, not quite there, but I'm getting there. And the other thing I'm working on is an episode about a company called San Sui that is a or was rather a company that made audio equipment like amplifiers and receivers and stuff like that. But as I was doing it, I felt like I was retreading some ground on a on a previous episode called how Speakers and Amplifiers Work? And I thought, why not have that episode play out? And then next week's Monday's episode will be about San Sui, and I won't have to to cover quite as much of the same territory again. I can focus more on the company in its history because y'all know me. Y'all know that if I start talking about a company that makes a certain kind of tech or sort of a product that features certain tech, I'll end up talking about how the tech came about what it does all that kind of stuff, but I've already done that. So we're gonna listen to this episode how speakers and amplifiers work, and I'll be back at the end to kind of tease next week's episode on this topic. But sit back and enjoy this classic episode. Today we are going to continue our episodes about how speakers work and how they are able to take electricity and make those sweet, sweet sounds for your ear holes. So let us jump back with a quick explanation of the electro magna at is um. So, electricity and magnetism are very closely related, and you've likely done the simple physics exercise of creating a basic electro magnet. So you'll take something like an iron nail and you'll wrap insulated copper wire in a coil around the nails several times. The nail acts as a ferromagnetic core. The copper wire coil is a conductor, so connecting the ends of the copper wire to a battery will then allow current to flow through the wire. Middle flow from one end of the battery through the wire down into the other end of the battery. As it goes around this coil, the flow of electricity creates a magnetic field, the nail and coil will behave like a permanent magnet. Would it's an electro magnet, but it will behave like a permanent magnet with a north pole and a south pole. And if you brought it close to a permanent magnet, then the opposite poles would attract each other and the similar poles would repel each other. So if you brought the electromagnets more poll next to a permanent magnets north pole, it would push that other magnet away and the polls will not change. Because the source of electricity is a battery, and batteries provide direct current, which means the current is always going to flow in the same direction. It's never going to reverse. But if you hooked the same nail and coil up to a source of alternating current, things would be very different. With alternating current, the direction of the flow of electricity changes rapidly every second, and as the direction of electricity changes, it affects the magnetic field. With electricity flowing in one direction, the head of the nail might represent the north pole of the magnet, and when the electricity switches to the other direction, the head of the nail will become the south pole of the magnet, and vice versa. You have created a fluctuating magnetic field by running an alternating current through an electro magnet, and you can do some pretty cool stuff with a fluctuating magnetic field. For example, if you bring this apparatus close to a conductive material, you'll induce a change of voltage in that material, even without making physical contact between the two. So if you do this with a stable magnetic field, all you'll do is see a very short spike, but then it stops because the magnetic field is not fluctuating. To induce electricity to flow by changing voltage in this other conductor, the magnetic field has to be fluctuating, or the conductor has to be moving in and out of the magnetic field constantly. If you get two coils of copper wire and you make sure the second copper wire has twice as many coils as the first one, you can create a transformer. So imagine you've got your first coil of wire. Let's say it's got ten coils ten ten loops around its core, and you've got a second core with copper wire, but there are twenty loops around the second core if you run a current through the first coil, it will induce current to flow through the second coil. Moreover, the voltage in the second coil will be higher than the voltage in the first coil because the second coil has twice as many coils as the first one. So the more times you loop a wire around a core, the greater the change of voltage is going to be between coil number one and coil number two. This particular version of a transformer would be called a step up transformer because the secondary coil has more turns than the primary coil and steps up the voltage. If the opposite were true, if coil number one had ten coils or ten loops and coil number two had five loops, then that would be a step down transformer. You would lower the voltage from primary to secondary. Transformers are what made alternating current the more viable solution to supplying electricity to homes and businesses back in the early days. Because transmitting electricity was all about efficiency. How could you efficiently get electricity from a power plant to where it needed to be well? If you used alternating current, you could create transformers and you could step up the voltage to very high levels, and that meant that you could transmit power across power lines much more efficiently. If you didn't do that, you had so much power loss that you would have to have lots of different power generators throughout the region in order to supply all the power needs of your area, at least back in the old days of direct current, because it wasn't easy to step up the voltage. And again, high voltage makes it more efficient to transmit power across long distances, so in the early days, that's why a C went out over d C. These days, you could actually do things a little differently if you wanted to, and you could go with direct DC power if you really wanted to, but it would require a big overhaul of the infrastructure. But transformers made a C much more practical anyway. Electromagnets are pretty awesome now. With speakers, it's not so much about voltage and current as it is about making the diaphragm of the speaker move in precise ways. With speakers, the electrical current acts as both the carrier of information and the means to make the diaphragm move. So you start with a steady magnetic field inside the basket You can create that steady magnetic field either with permanent magnets like I mentioned before, or with electro magnets, but it remains the same no matter what. The north pole is always going to be the north pole. The south pole is always going to be the south pole. Inside the frame, that field does not change. The voice coil on the cone ends up receiving the variable current that came from the transmitter that represents the recorded sound. Now, remember the way we record sound, as we typically will something like a microphone, and a microphone is essentially a speaker in reverse. A microphone has a diaphragm in it that vibrates in the presence of sound waves. Those vibrations cause fluctuations inside an electric current. You might vary the resistance of the circuit, as we talked about with the the old Johan Philip Rice approach, and by varying those that electric resistance within the circuit, you can fluctuate the electric current and then you can send that to a speaker, though you would typically send it to an amplifier first, but we'll talk about that in a minute. The speaker then essentially reverses this process. It takes those fluctuations sends them through an electro magnet, which will generate a variable magnetic field in response, which then makes the cone vibrate within the speaker and essentially do the opposite of what the microphones diaphragm was doing and recreate the recorded sound. It's pretty cool and pretty elegant, really. So the electrical signal representing the recorded sound comes into the speaker, feeds into the voice coil creates this fluctuating magnetic field. The field interacts with the permanent magnetic field inside the basket, either pulling the diaphragm forward in the basket and us pushing air outward, or pulling the cone back towards the back of the basket and allowing air to come further in by creating that lower pressure. And these fluctuations happen at high frequencies, so the diaphragm is moving very rapidly inside the basket. It's not just pushing out then pulling in. It's doing this hundreds or thousands of times per second, and it increases or decreases the air pressure as the cone pushes those air molecules or suddenly moves away, creating more space for them. And because sound is vibration. Those air molecules carry the sound up to our ears, and then we rock out to a C d C or whatever band you happen to like. That isn't nearly as cool as a C d C. Now, keep in mind what I have described is how a driver works. A speaker can and often does have more than one driver, and drivers come in different shapes, sizes, and purposes. So let's talk a little bit about what those are and what they do, and why you need to have different ones in the first place. Actually, that last question is the easiest answer right away. Remember again, sound is vibration, and low frequency sounds have longer wave forms. The points of high and low pressure are further apart from each other than with high frequency sounds. If you could actually see the changes in air pressure due to sound, you would see that the low frequency sounds have these larger gaps between the high and low pressure points in the waves as they move out from the source of sound. So you need a cone diaphragm that can vibrate at a slower frequency and push air effectively at that speed. For that reason, you would typically go with a heavier, larger diaphragm, both because the wavelengths of sound are longer if you're looking at the lower frequencies, and because making the material heavy gives it greater inertia, it takes more force to move of the diaphragm, and it will move at a pace that will reproduce as low frequency sounds you want. This type of speaker falls into the whooffer or sub whiffer categories. These are the speakers that create the base sounds. A sub whiffer tends to handle frequencies from around twenty hurts to two hurts. Think of a hurts as how long it takes a wave to pass through a given point in one second, or how many waves can pass through a given point in one second. Al Right, guys, we got some more to chat about with speakers. Before I jump into that, Let's take a quick break to thank our sponsor. Human hearing ranges from twenty hurts, which is twenty waves passing a given point in one second, to twenty killer hurts or twenty thousand waves passing through a point in one second. This really tells you more about the wavelength of the wave itself and thus the frequency and then the pitch. Remember, the lower frequencies are the lower pitches. The higher frequencies are the higher pitches, and that's the frequency range for typical human hearing twenty hurts to twenty thousand hurts. Now, I can tell you from my experience using a frequency sweeper, which will slowly go through a selection of frequencies that is all set at the same volume, so you get a standard volume across all of them, that while I can technically hear stuff at twenty hurts, it's not until you hit a frequency of about fifty hurts that it quote unquote sounds loud to me, even though actual volume of the two tones remains the same, so the amplitude is exactly the same, But until you get to a frequency of about fifty hurts, it just doesn't sound loud to me because my ears are not great at picking up those lower, super low frequencies. Also, I should mention that while sound waves come in different frequencies, sound itself travels at a speed that is dependent upon the medium through which it travels. So, in other words, low frequency sounds and high frequency sounds travel at the same speed through the same medium. Otherwise you would have all the high pitched sounds hitting your ears before the low pitched ones and conducting an orchestra would drive you crazy. The speed of sound is defined as the distance traveled by a sound wave in a certain unit of time. But hey, Jonathan, some of you might be saying you were just talking about frequencies. If a high frequency sound has twenty sound waves pass a certain point in the second, and a low frequency sound has twenty waves passing that same point in the second, are they traveling at different speeds? No, they're not. This is easier to imagine if we take an analogy. So let's say you're standing on the side of the road. Every single vehicle going past you on this one way road is traveling at a smooth twenty miles per hour or about thirty two kilometers per hour if you prefer. But they're all going that speed. Doesn't matter what kind of card is, they're all going exactly twenty miles or thirty two kilometers per hour. Some of these vehicles are very tiny, little smart cars. Some of them are super long extended buses, but they're all traveling at that same speed. So even though they're going at the same speed, the buses take more time to pass you than the smart cars do because the buses are longer. In the time it takes one super long bus to go buy you, like the front passes you and you time it out. Maybe for smart cars could go buy you and that same amount of time, even though they're all going at twenty miles. The same is true with sound waves, so we're not just talking about speed but wavelength. So low frequency sounds and high frequency sounds are traveling at the same speed. It's just you can fit more of the waves in at that time than others because of the length. All right back to the speed of sound. Now, I cannot give you a standard speed of sound for all occasions because the speed of sound depends on a lot of little things, For example, how much moisture is in the air or how cold is the air. Sound passes through the air, and air is made up of gases, and gases are made up of molecules. So as you heat up a gas, the molecules move apart from each other and they bounce around more. They're more able to move. As gas is cool, the molecules pack around together and they move around less, so they get more tightly packed. So a cold gas will transmit sound at a slightly slower speed than a warm gas will. If the temperature outside is sixty eight degrees fahrenheit or about twenties celsius and the air is dry, sound will travel at one thousand per second or three forty three per second. And it doesn't matter what frequency sound waves you're working with, that's the speed they're going to travel at. And again, at different temperatures and there are different media, sound will travel at a different speed. All right. Now, let's go back to the different types of drivers. After you handled the sub whoffers and the whoofers, well, the whoffers will still handle lower frequencies, but subwhiffers are are specialized whoffers, largely because they will frequently be paired with special circuits and cabinets dedicated to creating those very very low frequencies in an effort to produce a specific quality of sound, such as let's say you're watching an action film and something done blowed up real good. You want to have that rumbly low base for those moments, you know, the kind where you can actually feel it because it's vibrating the chair and the air around you, and so it's it's that kind of rumble you can feel in your chest. Well, that frequently means you need a dedicated subwhoffer unit that has its own power supply to generate the vibrations with enough force necessary to create that effect. So it's not just the speed but how hard it's pushing. After subwhiffers and whoffers, you've got mid range drivers or mid range speakers, and as the name suggests, these drivers are responsible for producing sounds in the middle range frequencies of human hearing. A typical range might include two fifty hurts to two thousand hurts. You may have also the term squawker when referencing mid range speakers. They're made of lighter materials and they can vibrate at higher frequencies than whiffers and subwhiffers, which is necessary to create those mid range tones. And then you have tweeter speakers. These are made of the lightest weight material and they vibrate the fastest in an effort to reproduce frequencies on the upper levels of human hearing, which tends to be between two thousand and twenty thousand hurts at least for consumer speakers. There are tweeters that can be made for special purposes that can generate sound frequencies well above the range of human hearing, some of them as high up as a hundred kill hurts or one hundred thousand hurts. That's five times higher than the highest frequency the average human is capable of perceiving. So why would you want a tweeter that could go beyond the range of human hearing. Well, you might use it for scientific research purposes, like finding out what high high high pitches the ultrasonic pitches might due to affect animal behavior. So you might be able to do that to learn how high a pitch a dog might be able to hear, for example, because dogs can hear at a different range than humans can. Or you might want to do experiments to see if those imperceptible frequencies have an effect on the sounds we can here. So there are audio files who insist that frequencies beyond the human range of hearing can change the quality of the sounds that we do here, and thus it's imperative to get a sound system and a type of media capable of reproducing sound frequencies at every level if you want a true reproduction of an original sounds quality. This falls into the realm of psychoacoustics the study of sound perception. Because hearing involves processes in the brain, there is a subjective component to it that cannot be easily described through physics. We can talk all about the physics of sound waves and sound propagation, but ultimately, when it comes to the way we experience sound, we have to take gray matter into account, and that gets tricky since our experience of perceiving sound can depend upon other things unrelated to the actual physics of the sound itself. For example, if I were to tell you that I have a sound system, and I've set it up and it consists of the most expensive and most technologically advanced components, and the media that was going to play represented the most true reproduction of an actual sound, that might be enough to influence your perception of the sound. Even if what I was really using was just good equipment, not the best, but just good stuff. Even if all all that stuff I told you wasn't true, your perception of sound might make it seem like you're listening to the most perfect reproduction of the original performance as could be attained. Or if I did play a sound back on what really was an amazing sound system, but Before I did it, I made a whole bunch of apologies for how the system I was using could not faithfully represent high tones, or had a very weak base output, or something like that. You might perceive the playback as fall lewing these trends that I had mentioned, even if scientific recording instruments were to show that the playback didn't suffer from those problems at all. All that being said, the psychological aspect of how we perceive sound does have limitations. No amount of snake oil salesmanship is going to convince you that a truly subpar stereo system is capable of reproducing the glory of the Philharmonic Orchestra, for example. But because there is the subjective element and how we perceive sound, there's the opportunity to exploit that element and make a lot of money in the process. I've talked before about how certain manufacturers have used this to market high end audio equipment, and some of that has little to no scientific evidence to back up the claims that they make about those gadgets, and yet they're able to set exorbitant prices for components that audio files will cover it because they're always in a quest to get that perfect representation of a sound. Uh, so this stuff does happen. I also covered this when I talked about MP three compression, because if you remember an MP threes, part of the compression strategy is to take all the different parts of a sound that we humans typically don't notice, and you just cut them. You get rid of them, because that way you cut down on the size of the sound file. The strategy is, if you can't perceive it, then we don't need it in the information. We can just cut it that. Audio files say no, if you do that, it affects the stuff that we can here, and thus you are changing the nature of the audio recording. Just because you couldn't hear the thing doesn't mean the thing wasn't doing something else. I think the jury is still out on that in a large part. I mean, there are some legitimate arguments to make about harmonics and things that do come into play, but I'm not sure it gets to the level of subtlety that a lot of audio files argue. At least I don't see the scientific evidence supporting it. That doesn't mean it's wrong, It just means I haven't seen the evidence supporting it. Anyway, As soon as we come back. I'm gonna go into talking about amplification and why that's important, but first let's take another quick break to thank our sponsor. All right. Now, Back when I was talking about the development of the loud speaker, I mentioned that Rice and Kellogg observed there needed to be advancements in amplification, and by that they meant there needed to be a way to boost the electrical signal from the risk the transmitter the microphone in order to give a speaker enough umph to vibrate at a force strong enough to play back the sounds at a suitable volume. Without amplifiers, the signal strength might only allow a speaker to play back a sound at a low volume, or if the signal is very weak, it might not even move the speaker significantly enough at all to create any real sound. The reason the signal tends to be weak goes back to the limitations we face when we record sound in the first place. So using the microphone effect, we transform sound into electrical signals by making the microphones diaphragm vibrate, mimicking the way our ear drums work. Right, So it's like we're speaking into someone's ear. When we talk into a microphone. Then we transform sound into electrical signals by making that microphone diaphragm vibrate, and those small vibrations introduce fluctuations into an electrical signal in some way. But for sound to affect the diaphragm at all, the diaphragm has to be very lightweight, very sensitive, and it has to make very small movements. Otherwise we'd have to make sound an enormous amplitudes or volume in order to generate the force necessary to vibrate the diaphragm. So it has to be very lightweight, very very sensitive, and it's moving in a very small distance, so it can only make tiny changes in electrical current or generate a very tiny electrical current. Now that's good enough for the purposes of recording the sound. You can do that. You can use that to record sound. It's fine because it can record at those tiny details. But if you want to play the sound back on a speaker, you have to boost that signal in order to drive the speakers to physically move them. You want to make the signal more powerful, but you also want to keep all the fluctuations of the signal, all the dynamics of the signal, So that way, you can represent when a song gets louder or more quiet, or when one element is taking over over another element. All of these things are very subtle, and you have to preserve that. So you want the signal not just to be boosted, but for all the different fluctuations of that signal to be represented in that boost. You want it all to be at the same relative strength as they were in the weaker signal. Now, an amplifier does this through the use of two separate circuits. The first circuit is the input circuit. That's the weaker of the two signals, that's the one that's coming from the microphone. The second circuit is your output circuit, which sends a stronger signal out to this speakers, and it draws upon the amplifier's power supply to boost the signal. So you have an amplifier, it has its own power supply. It's generating the signal that's going through this output circuit. The power going through the output circuit is a direct current, so it's flowing in a set direction. It does not change. If you have an amplifier and you've hooked it directly up to your house, is alternating current there's a power supply element inside the amplifier that converts it from alternating current to direct current. Now, think of the output circuit as always pushing a strong signal out towards the speakers. It's just most of the time this signal is not carrying any information. But when the amplifiers on, that's what's doing. It's pushing the strong signal out to the speakers. The input circuit's job is to use the original weak electrical signal as a way to vary the resistance in the output circuit, so the variable resistance recreates the voltage fluctuation in the original signal. So what you're doing is you've got this strong signal going out, use the weak signal to introduce the same fluctuations into the strong signal, and then the strong signal will reflect the weaker one. It will be exactly the same, except stronger. In the good old days, amplifiers relied upon vacuum tubes as an integral component, and in fact some amplifiers still do, particularly for stuff like professional electric guitar amplifiers. There are professional musicians who swear by vacuum tube amplifiers and they will not use anything else. Vacuum tubes are pretty interesting technology, and they date back to the early twentieth century. So let's talk about how they work for just a second. First, they look a lot like light bulbs, and in fact they operate very similar to light bulbs. They are glass tubes. Inside this glass tube is a filament like a light bulb. The filament inside uses electrical resistance to heat up. The filament either content aines or is somehow wrapped around a material like tungsten, which, when it's heated to very high temperatures, starts to boil off electrons. That would be the cathode of the vacuum tube. It's the source of electrons. The electrons accept only so much energy, and then after that they effectively jump ship. They're ready to burst off of the atoms that they were previously connected to. Now, also inside the vacuum tube is a plate that has a relative positive charge to it compared to the cathode. That's called the anode. The electrons are negatively charged, and so they're attracted to the positively charged anode, and the negative charged electrons flow towards the positively charged anode. Now, if this were all, there were to a vacuum tube, it would just be a diode. That means it would be an element in a circuit that would allow electricity to pass one way from the cathode to anode, but not back the other way. However, there's a third element, and that's what creates the amplification sho effect. That element is a grid of spiral wires or a mesh material. The acts as a sort of control grid or cage between the cathode and the anode, so it essentially surrounds the cathode. Now, if you apply a voltage to this control grid that is lower than the cathode itself, it reduces the amount of current passing from cathode to anode. By placing a large positive voltage on the plate and then feeding a signal to the control grid, you can affect the voltage across the load on the circuit. So you make tiny changes in the control grid's voltage and you get a much larger change across the load of the circuit amplifying the signal. So again, you you put a large positive voltage on this plate, you feed the input signal into the the control grid, and then you amplify that signal across the entire load, and that load would it typically involve speakers or an amplifier or These days most amplifiers do not use vacuum tubes. Instead, we use solid state transistors. To describe all those transistors work gets a little complicated, but in general, and basic transistor has three components. You've got an emitter, a base, and a collector. The emitter and the collector are both in type UH semiconductors, meaning that they have more electrons. They have a surplus of electrons there. You can think of it almost like a negative charge. The base is a P type semiconductor. It's sandwiched between the emitter and the collector. It has what would we would call a positive charge or holes for electrons. Feeding the input current between the emitter and the base creates a much larger output current between the emitter and the collector, thus amplifying the signal. Now, the output signal should ideally match the input signal exactly, except again everything is just bigger as an amplified and that signal would be strong enough to do the work of moving those speaker diaphragms and generating the sounds we enjoy. Well, I hope you enjoyed health speakers and amplifiers work. Like I said, next week we're going to have the story of San Sui and it's rise and fall and what the company did and UH the various products that it produced and why they were important. Why certain audio files to this day, we'll seek out San Sui UH components like receivers in particular, there's certain receivers that are highly prized among audio files. Even though spoiler alert, this company doesn't exist anymore. So that will be next week's episode. But I'm glad that I did this so that way you know, I'm not just repeating something I've already done in the past. I know that can be very frustrating, and due to my terrible memory, it happens pretty frequently without me even being aware of it. So I hope you enjoyed this episode. If you have suggestions for future topics, because San Sui is actually going to be that's a listener request. I'll talk about that more next week. So if you have a request, like if there's a specific topic in tech you want me to talk about. Maybe it's a particular company, a trend in technology of particular type of tech, and you want to know more about it, send me a message. I love getting those. It always gives me a great starting point to jump into some research, and the best way to do that is to send it over on Twitter. The handle for the show is tech Stuff hs W and I'll talk to you again really soon. Tech Stuff is an I Heart Radio production. 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